The present invention relates to an improved hydraulic engine mounting device and specifically a hydraulic engine mount, which is simpler to construct and assemble than prior art devices.
An automobile engine is subject to complex vibration effects that produce multiple combinations of forces. As such it is necessary to insulate the automobile from engine vibrations and unwanted movements of the engine with an antivibration system. Such a system reduces the vibrations to relatively small spring forces, which are transmitted to the support mountings.
Engine mounting systems have progressed from simple rubber components to engineered fluid powertrain mounts. Relatively all engine support mounts feature rubber or another elastomeric compound as comprising at least a portion of the spring medium for the support. It is resilient by virtue of its high deflection to load ratio. Rubber also has an inherent self-damping effect that helps prevent resonant vibration.
The typical hydraulic mount includes a pumping chamber surrounded by relatively thick elastomeric walls with an orifice track extending between the pumping chamber and a reservoir that is generally surrounded by a flexible rubber diaphragm. The reservoir is typically located on the opposite side of a partition from the pumping chamber. When load is applied to the hydraulic mount, compression of the mount pressurizes the fluid in the pumping chamber. The pressurization causes the fluid to flow through the orifice track to the reservoir. When load is removed, i.e. during a rebound situation, fluid is drawn back to the pumping chamber from the reservoir. The geometry of the pumping chamber, orifice track and reservoir are typically tuned for specific applications so that the fluid in the orifice track resonates at certain frequencies. Thus, a peak damping effect at a selected frequency can be achieved resulting in a reduction in the harshness of a vehicle ride from both road and engine induced vibrations. As such, some form of hydraulic mount is generally preferred in most applications.
However, hydraulic mounts are generally costly and/or difficult to assemble. A hydraulic (or fluid tight) seal must be achieved between the pumping chamber and the reservoir. This seal must also be able to withstand the pressures within the pumping chamber. To-date, the seal between the pumping chamber and the reservoir has used the perimeter edge of the rubber diaphragm (which often defines the periphery of the pumping chamber) as a fluid seal. However, constructing the fluid seal has typically added to the cost of the hydraulic mount.
As can be seen from FIGS. 1A-1D, the added cost comes from added material costs, added labor costs to construct, or a combination thereof. FIG. 1A shows a rubber diaphragm 110a of which the edge portion must be wrapped around an orifice assembly 120a before the remainder of the hydraulic mount is assembled. In a variation of FIG. 1A, FIG. 1D also shows the edge of rubber diaphragm 110d wrapped around the base plate and held against the orifice assembly 120d. Both of these variations are expensive to assemble. FIG. 1B shows a recessed trough in orifice assembly 120b within which the edge of rubber diaphragm 110b is placed. Machining a trough or casting a trough in orifice assembly 120b adds significantly to the overall cost. The rubber diaphragm 110c of FIG. 1C has a metal ring 140c molded into the edge portion. Molded metal ring 140c provides structure to that portion of the diaphragm to keep diaphragm 110c in place. Such a metal ring adds significantly to the manufacturing costs of the diaphragm and thus to the overall costs of the hydraulic mount.
Accordingly, it is a feature of the present invention to provide a hydraulic mount that overcomes the disadvantages of prior art hydraulic mounts in that a hydraulic mount is economically manufactured and assembly is simplified. This result is preferably accomplished with use of a orifice assembly that includes a ledge. The ledge cooperates with a fluid sealing surface of, preferably, the diaphragm resulting in a fluid seal and a hydraulic mount that is easy to assemble and inexpensive to manufacture. The hydraulic mount of the present invention requires no additional parts and the entire hydraulic mount can be assembled by simply dropping each of the component parts into place and crimping the perimeter.
This feature, along with other features in the present invention, is achieved in a hydraulic mounting device which comprises a main body defined by a shell. This shell includes first and second portions as well as first and second chambers within the shell. The first chamber is separated from the second chamber by an orifice assembly. The first shell portion includes a flange portion for supporting the orifice assembly, the flange portion having a plastically deforming perimeter. The second shell portion interengages with the first shell portion at the flange portion. A diaphragm is interposed between the second shell portion and the orifice assembly within the second chamber. The orifice assembly includes a ledge portion extending about an outer perimeter of the orifice assembly. In a preferred embodiment the perimeter of the diaphragm is captured between the ledge portion and the perimeter of the second shell portion. The plastically deforming perimeter of the first shell is used to compress the diaphragm between the orifice and the second shell to provide a hydraulic seal. In a preferred embodiment of the invention, the ledge portion includes a step portion of a stamped plate together with an outer perimeter edge of a smaller plate.
In accordance with another aspect of the invention, an orifice assembly for a hydraulic mount is provided. The orifice assembly is used to separate the mount into a first chamber and a second chamber. The orifice assembly comprises at least a first plate of a first diameter and a second plate of a second diameter, the first diameter being larger than the second diameter and each of the plates including first and second orifice areas with openings which cooperate to define a fluid path between the first and second chambers. The step portion on a outer portion of a first plate cooperates with an outer perimeter edge of the second plate to create a ledge portion on a outer perimeter of the orifice assembly. In a preferred embodiment of the invention, the first plate includes an interior portion and the step portion includes a riser portion extending radially outward from the interior portion. A tread portion extends radially outward from the riser portion, the outer perimeter edge of the second plate being generally radially aligned with the riser portion.
Another aspect of the invention includes a method of constructing a hydraulic mount. This method comprises providing a main body including a first and second shell portions each having an outside diameter. It includes providing a flange portion for supporting the orifice assembly on the first shell portion and providing a flange portion with a plastically deforming perimeter on its outside diameter. An orifice assembly is provided which has an outside diameter and has a ledge portion extending about an outer perimeter of the orifice assembly which terminates at its outside diameter edge. Finally, an elastomeric diaphragm is provided. It has an outer edge area terminating in an outside diameter generally the same as the outside diameter of the second shell portion and the outside diameter of the orifice assembly.
The hydraulic mount can be assembled while submerged in fluid or the mount can be assembled dry and then filled with fluid after assembly. In a preferred embodiment, it is an antifreeze such as ethylene glycol. The orifice assembly is then placed within the first shell portion with the outer perimeter of the orifice assembly sitting on the flange portion of the first shell. The diaphragm is then placed on the ledge portion of the orifice assembly and the second shell portion is placed over the diaphragm. The outer edge area of the diaphragm is captured between the second shell portion and the ledge portion. The plastically deforming perimeter of the first shell is then bent radially inward onto the second shell portion. This compresses the diaphragm sufficiently to provide a hydraulic tight seal (or fluid seal) at the ledge portion of the orifice assembly. Each of the described components is preferably sized for easy vertical self centering assembly.
Thus it is a principal object of the present invention to provide a hydraulic mount which is easily assembled and yet provides a robust and secure hydraulic seal.
It is yet another object of the present invention to provide a hydraulic mount which is designed for quick and easy vertical self centering assembly.
Still another object of the present invention is to provide an improved hydraulic mount which is manufactured with lower cost, easily produced parts.
These and other objects of the invention will become apparent to those skilled in the art upon reading and understanding the following detailed description of the invention.